Ionic Conductivity Measurements Research Articles

Synergistic effects of polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP) blends in gel electrolytes for efficient and long-term stability in dye-sensitized solar cells (DSSCs)

In this work, the stability issues associated with liquid electrolyte-based dye-sensitized solar cells (DSSC) have been addressed by introducing polymer gel electrolytes. The synergistic combination of polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP) has been achieved through solution blending. Ionic conductivity measurements, scanning electron microscopy, X-ray diffraction analysis, and Fourier transform infrared spectroscopy have been employed for analysis. Optimal cohesiveness was observed at PVP concentrations exceeding 40 %, with the best outcomes achieved at a 50 % PVDF-PVP weight ratio. The electrolyte solution, comprising the polymer blend, suitable solvents, and iodine-based salts, exhibits peak conductivity (2.33 mScm⁻1) at a 10 % salt content. DSSCs utilizing the PVDF & PVP polymer blend gel electrolytes demonstrate enhanced durability and maintained efficiency at 5.43 %, exhibiting only a modest 12 % reduction compared to liquid electrolyte counterparts. Over two weeks, the fabricated DSSCs exhibited consistent photovoltaic performance, while conventional cells experienced significant declines in short-circuit current (36 %) and open-circuit voltage (33.33 %). This study signifies a promising advancement in solar cell technology, showcasing improved stability and performance in DSSCs using conductive polymer blend gel electrolytes.

Quantifying Resistive and Diffusive Kinetic Limitations of Thiophosphate Composite Cathodes in All-Solid-State Batteries

Increasing the specific capacity and rate performance of thiophosphate composite cathodes is a major challenge in solid-state battery development. Understanding the charge transport kinetics and rate-limiting mechanisms within the cathode is key towards efficient optimization. Herein, we use quantitative analysis of chronoamperometric rate performance data to differentiate between resistive and diffusive rate limitations of NCM811—Li6PS5Cl cathodes with different morphology and composition. We substantiate our findings with separate measurements of the effective ionic conductivity and Li+ diffusion coefficients using impedance spectroscopy and GITT techniques, respectively. Increasing the active material to solid electrolyte ratio is found to increase diffusive limitations, which originate from the small contact area between the active material and solid electrolyte. The diffusive limitation is especially pronounced for single crystal NCM811 cathodes at over 84% AM. Employing fine particle catholyte significantly increases the contact area, alleviates the diffusive limitation, and increases rate performance. These results provide guidelines towards bringing the solid-state battery performance levels closer to practical targets.

Use of natural dyes to color metakaolin-based geopolymer materials

Over the years several colored ceramic-like materials have been prepared by using many synthetic dyes, which are toxic and polluting. Up to date, no studies have been reported on the combination of natural dyes within the geopolymers (also known as amorphous aluminosilicate polymers). In this scenario, natural dyes such as curcumin, chlorophyll, and a freeze-dried grape marc from the wine agrifood supply chain have been employed to investigate their effectiveness ability to color metakaolin-based geopolymers. The colored geopolymers, cured at 25 or 40 °C for 24 h, are characterized after 56 days of ageing time at room temperature by the ionic conductivity and pH measurements, Fourier-Transform Infrared spectroscopy, compressive strength, and color assessment by the color space analysis before and after soaking the samples in water. Eventually, the control geopolymer samples are also characterized for their potential antimicrobial and cytotoxicity properties. The main findings revealed that employing natural dyes to color geopolymers offers a promising alternative to toxic synthetic dyes. The samples retained their color for brief time when exposed to water thus suggesting indoor application. Moreover, all the samples exhibited good geopolymerization as confirmed by FTIR analysis. Notably, samples cured at 25 °C showed better compressive strengths compared to those cured at 40°C. Finally, the bioimpact of these materials suggests that the synthesis in loco of geopolymers is safe for the operator.

Fluoride Ion in Alcohols: Isopropanol vs Hexafluoroisopropanol.

The utility of alcohol as a hydrogen bonding donor is considered a providential avenue for moderating the high basicity and reactivity of the fluoride ion, typically used with large cations. However, the practicality of alcohol-fluoride systems in reactions is hampered by the limited understanding of the pertinent interactions between the OH group and F-. Therefore, this study comparatively investigates the thermal, structural, and physical properties of the CsF-2-propanol and CsF-1,1,1,3,3,3-hexafluoro-2-propanol systems to explicate the effects of the fluoroalkyl group on the interaction of alcohols and F-. The two systems exhibit vastly different phase diagrams despite the similar saturated concentrations. A combination of spectroscopic analyses, alcohol activity coefficient measurements, and theoretical calculations reveal the fluorinated alcohol system harbors the stronger OH···F- interactions between the two systems. The diffusion coefficient and ionic conductivity measurements attribute the present results to disparate states of ion association in the two systems.

Dynamics of Novel Zinc Ion Electrolytes

Zinc ion batteries are a niche alternative for battery applications. Their implementation is however afflicted by several factors, one of which is the need for more efficient electrolytes. Deep eutectic solvent (DES) electrolytes based on ZnCl2salt offer many attributes including, including improved stability and reduced dendrite formation. In this work we will present a molecular level understanding of the ion dynamics in electrolyte mixtures based on ZnCl2 and various co-solvents including organic carbonates and water. Focus is on the ion dynamics as interrogated by 1H NMR spin-lattice relaxation times (T1 ) combined with ionic conductivity, viscosity and density measurements. As shown in Figure 1, preliminary T1 results infers multiple ionic coordinated species with varying rates of mobilities that are co-solvent dependent. Additionally, data shows selective interaction sites between the hydrogen bond donors and acceptors, as well as the co-solvents. Figure 1. 1H T1 for the null and AcN co-solvent mixtures of (a) 1ZnCl2:4EtG and (b) 1ChCl:1ZnCl2:6EtG. Figure 1

Investigation of KOH‐doped PVA‐based membrane electrolytes cross‐linked with tartaric acid for DMAFCs

AbstractThis research focused on the development of anion exchange membrane electrolytes suitable for direct methanol alkaline fuel cells (DMAFC) by employing a straightforward blending and solution casting process complemented by subsequent heat treatment. Tartaric acid (TA) was employed as a cross‐linking agent to enhance the heat resistance and structural integrity of the PVA matrix. The distinctive attributes of the PT (PVA and tartaric acid blend) samples, including water absorption and swelling capacity, were comprehensively investigated with respect to variations in both TA content (expressed as wt. % relative to the PVA matrix) and alterations in the duration of thermal treatment. Cross‐link formation between the polymer chains and TA was determined using FTIR analysis. The samples were subjected to comprehensive analysis, encompassing the determination of crystallinity via X‐ray diffraction (XRD), assessment of thermal stability using thermogravimetric analysis (TGA), investigation of morphology through scanning electron microscopy (SEM), and measurement of ionic conductivity using AC Impedance spectroscopy. The methanol permeability was measured to determine the selectivity values of the membranes. Subsequently, within the DMAFC system, the performances of the PT30‐3, PT40‐2, and PT40‐3 membranes, which exhibited the highest selectivities, were assessed. The contribution of the crosslinking process to the resistance of the membranes to oxidative conditions, as represented by the Fenton solution, was evaluated to assess the chemical stability of the membranes. The maximum power densities for PT30‐3 and PT40‐3 membranes reached 15.29 and 12.53 mW/cm2 at 30°C, respectively. These figures exhibited a notable increase, reaching 32.73 mW/cm2 for PT30‐3 and 31.72 mW/cm2 for PT40‐3 when the temperature was elevated to 60°C. This study confirmed that the crosslinking strategy using TA assisted by thermal treatment is very simple and competitive compared with other techniques reported in the literature. PT membranes are promising candidates for commercialization and utilization in DMAFC owing to their environment‐friendly nature, cost‐effectiveness, and high efficiency.Highlights TA cross‐linking improved the thermal and dimensional stability of PVA. The PT membrane properties varied with TA content and thermal treatment time. Some electrolytes in this study outperformed those previously reported for DMAFC. PT membranes offer efficiency, cost‐effectiveness, and eco‐friendliness for DMAFCs.

Effects of operating temperature on Li-O2 battery with ionic liquid-based binary electrolyte

Awaiting a breakthrough, the Li-oxygen battery (LOB) is considered a promising candidate to meet the high energy demands in the future. Among various critical challenges which hamper its development, the mystery of the electrolyte with optimal properties remains unsolved to this day. In this study, we comprehensively investigated the effects of operating temperature (20C, 40 °C and 60 °C) on the electrochemical performance of LOBs incorporated with room temperature ionic liquid (RTIL) and organic solvent binary electrolyte. We designed and investigated 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][Tf2N]) RTIL and dimethyl sulfoxide (DMSO) organic solvent at various volume ratios ((4:1), (1:1), (1:4)). Among the binary electrolytes, ([C2C1im][Tf2N]/DMSO (1:4)) delivered the highest discharge capacities of 3.70 Ah g− 1 (20 °C), 4.0 Ah g− 1 (40 °C) and 3.65 Ah g− 1 (60 °C) as compared with pure [C2C1im][Tf2N] and DMSO. Cycling stability tests showed superior stability of the binary electrolyte ([C2C1im][Tf2N]/DMSO (1:4)) irrespective of the operating temperature. From viscosity and ionic conductivity measurements (at 20–60 °C), [C2C1im][Tf2N]/DMSO (1:4) exhibited the highest ionic conductivity and the lowest viscosity compared with other binary electrolytes (even with pure electrolytes) at any given temperature. Cyclic voltammetry (CV) tests revealed the highest reaction rates for [C2C1im][Tf2N]/DMSO (1:4) binary electrolytes than pure electrolytes. The superior performance of [C2C1im][Tf2N]/DMSO (1:4) binary electrolyte was ascribed to enhanced stability against reactive intermediate species during oxygen reduction reaction (ORR), increased ionic conductivity, low viscosity (comparable with organic electrolytes), improved oxygen solubility, and relatively low evaporation rates.

Vertex Differentiation Strategy for Tuning the Physical Properties of closo-Dodecaborate Weakly Coordinating Anions.

We report the synthesis and characterization of various compounds containing the 1,7,9-hydroxylated closo-dodecahydrododecaborate (B12H9(OH)32-) cluster motif. Specifically, we show how the parent compound can be synthesized on the multigram scale and further perhalogenated, leading to a new class of vertex-differentiated weakly coordinating anions. We show that a postmodification of the hydroxyl groups by alkylation affords further opportunities for tailoring these anions' stability, steric bulk, and solubility properties. The resulting dodecaborate-based salts were subjected to a full thermal and electrochemical stability evaluation, showing that many of these anions maintain thermal stability up to 500 °C and feature no redox activity below ∼1 V vs Fc/Fc+. Mixed hydroxylated/halogenated clusters show enhanced solubility compared to their purely halogenated analogs and retain weakly coordinating properties in the solid state, as demonstrated by ionic conductivity measurements of their Li+ salts.

Effects of Operating Temperature on Li-O2 Battery with Ionic Liquid-Based Binary Electrolyte

The progress of rechargeable Li-O2 battery (LOB) is hampered due to the number of challenges its components present. Among various critical challenges, the choice of electrolyte has always been a bottleneck impeding the breakthrough in the development of LOB. Various electrolytes, including organic solvents and room-temperature ionic liquids (RTILs) have been developed and studied. Each electrolyte comes with various limitations, which restrict its application in the LOB. These include thermal and electrochemical stability, volatility, viscosity, flammability, capability to dissolve incoming oxygen, diffusivity, and ionic conductivity. Consequently, no electrolyte could be regarded as an ideal electrolyte. Nonetheless, efforts have been made to tune the physiochemical properties of the electrolyte by blending two or more miscible solvents. High thermal and electrochemical stability and negligible volatility of RTILs can be combined with high diffusivity and ionic conductivity of organic solvents by merely blending them with optimized volume ratios.In this study, we comprehensively investigated the effects of operating temperature (20°C, 40°C and 60°C) on the electrochemical performance of LOBs incorporated with RTIL and organic solvent binary electrolyte. We designed and investigated, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][Tf2N]) RTIL and dimethyl sulfoxide (DMSO) organic solvent at various volume ratios ((4:1), (1:1), (1:4)). Among the binary electrolytes, ([C2C1im][Tf2N]/DMSO (1:4)) delivered the highest discharge capacities of 3.70 Ah g-1 (20°C), 4.0 Ah g-1 (40°C) and 3.65 Ah g-1 (60°C) as compared with pure [C2C1im][Tf2N] and DMSO. Cycling stability tests showed superior stability of the binary electrolyte ([C2C1im][Tf2N]/DMSO (1:4)) irrespective of the operating temperature. From viscosity and ionic conductivity measurements (at 20-60°C), [C2C1im][Tf2N]/DMSO (1:4) exhibited the highest ionic conductivity and the lowest viscosity compared with other binary electrolytes and pure RTIL at any given temperature. Cyclic voltammetry (CV) tests revealed a higher reaction rate with [C2C1im][Tf2N]/DMSO (1:4) binary electrolytes than pure electrolytes. The superior performance of [C2C1im][Tf2N]/DMSO (1:4) binary electrolyte was ascribed to enhanced stability against reactive intermediate species during oxygen reduction reaction (ORR), increased ionic conductivity, low viscosity (comparable with organic electrolytes), improved oxygen solubility, and relatively low evaporation rates. The detailed results and discussion will be presented during the presentation.

Electrochemical Characterization of Thiophosphate- Ionic Liquid Hybrid Lithium Electrolytes Against Li Metal

(Almost) solid-state batteries that utilize thiophosphate solid electrolytes (SE) are an exciting technology emerging as a potential alternative to lithium-ion batteries. When used alongside a lithium metal anode they can offer the high energy densities [1] required to meet the increasing demand for energy storage. However, they suffer from numerous issues which predominately occur at the cathode- or anode-SE interface. Issues include dendrite propagation through gaps, pores and grain boundaries of the solid electrolyte which can eventually puncture electrolyte crystallites and lead to cell failure. [2] Thiophosphate electrolytes are also unstable both chemically and electrochemically. As a result of the SEs having a low electrochemical stability window reduction or oxidation can occur at the anode or cathode interface, forming a resistive solid electrolyte interphase (SEI). [3] Finally, the ionic contact between Li metal anode and electrolyte is poor and thus high interfacial impedances can arise. These impedances can be dynamic which increase during stripping of the lithium and decrease during plating. [4] To solve some of the interfacial issues there is the option to add a small of amount of liquid electrolyte at the lithium metal-electrolyte interface. The liquid electrolyte can fill in the gaps and pores at the interface thus improving the ionic contact whilst allowing a more stable interface. Whilst the ionic contact can be improved the inherent instability of thiophosphate electrolytes against the liquid electrolyte means that a new interphase known as the solid-liquid electrolyte interphase (SLEI) can form. The presence of this interphase can therefore lower the energy density and round-trip efficiencies of cells which utilize hybrid electrolytes meaning that minimizing the SLEI resistance and maximizing total ionic conductivities is important in hybrid cells. [5]In this work a hybrid of the thiophosphate argyrodite Li6PS5Cl and the ionic liquid x-LiTFSI-1-butyl 1-methylpiperidinium TFSI (BMPipTFSI) with LiTFSI concentrations of 0.25 M and 0.5 M was studied. The choice of SE and liquid electrolyte boils down to the high ionic conductivity of the SE and the electrochemical and thermal stability of the ionic liquid. Temperature-dependent ionic conductivity measurements showed that hybrid systems exhibit lower in room temperature ionic conductivities and higher total activation energies. This hints at the presence of a SLEI forming between the LE and SE. To study how the SLEI resistances changes over time, ion blocking potential impedance spectroscopy measurements were performed. These measurements were performed at 10 °C to allow for the resistance contributions to be better resolved and showed a SLEI resistance of around 45-50 Ω cm2 for both hybrids. Over the period of 130 hours this resistance changed minimally (around 5 Ω cm2 on average) indicating good stability of the SLEI. To further test the suitability of this hybrid alongside lithium metal anodes impedance measurements in symmetrical lithium cells (Li0|LE|LPCL|LE|Li0) were undertaken. In this case galvanostatic impedance spectroscopy (GEIS) with an applied current density of ±0.4 mA cm-2 was used to probe the changes in resistance contributions in the system over the period of stripping (positive current) and plating (negative current). For cells with just SE a large change in the resistance owing to the electrochemical reaction (ECR) (Li0 ↔ Li+ + e-) occurred during stripping and plating indicating the dynamic nature of the ionic contact at the interface. For the hybrid electrolyte cells, this ECR resistance is decreased and becomes more stable however a larger interphase resistance is present. This resistance is a combination of the resistances of both the SLEI (the interphase between the LE and SE) and the SEI (the interphase between LE and Li anode) and it changes over stripping and plating showing that the S(L)EIs which are present are dynamic. Finally, post-mortem SEM/EDX of the surface of samples show a change in morphology and the presence of decomposition products from both the liquid and solid electrolytes. These studies show that the LPCL-BMPipTFSI hybrid is stable and improve ionic contact at the lithium metal anode interface. Further testing in half Li-S cells will determine the suitability of the use of the ionic liquid at the cathode side of the cell.

Poly(vinylferrocene) as an Ionomer and Sulfur-Confining Additive for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising owing to their high energy density, environmental benignity, and low cost. Most of the commonly used binders in Li-S battery cathodes are inert and have no significant effect on the challenges of sulfur as a cathode material, such as the polysulfide shuttle effect, low ionic/electronic conductivity, and a sluggish redox reaction. In this work, we demonstrate the use of poly(vinylferrocene) (PvFc) as a binder additive that can effectively increase the ionic conductivity of the cathode and act as a sulfide-confining agent. Electrochemical tests performed with PvFc as part of the binder mixture used to cast the cathodes demonstrate an increase in rate capability and cycle life when compared to the baseline samples. Ionic conductivity measurements and X-ray photoelectron spectroscopy suggest that the π-cation molecular interaction between the cyclopentadienyl rings from ferrocene and Li+ behaves like an ion couple with ferrocene acting as a static, covalently bound acceptor of Li+ ions that enhances their mobility through the cathode. This coupled with the affinity between the ferrocenyl cations and the Li salt anions, which provides more distribution of counterions for Li+ movement and improves accessibility to the cathode S reservoir, make PvFc a promising ionomer for Li-S batteries. In addition, the π-cation bonds between cyclopentadienyl and lithium polysulfides produce a sulfide-confining effect that mitigates capacity fade through polysulfide dissolution. This work demonstrates an expansion in the utility of PvFc as a component in Li-ion batteries, which so far is mostly limited to use as an active material in organometallic batteries.

Measuring the ionic conductivity of solid polymer electrolyte powders

Ex-situ characterization of solid polymer electrolytes plays an important role in their development as materials for energy applications, with ionic conductivity being a crucial parameter to quantify. Conventional measurements of ionic conductivity often require the formation of a free-standing polymer film which in many instances is difficult to fabricate, thus there may be a need to quantify their ionic conductivity in powder form. In this work, we present a practical and reproducible method for measuring the ionic conductivity of solid polymer electrolytes (SPEs) in their powder form. By using a modified configuration of a through-plane cell, demonstrated with both a proton conducting- and an anion conducting-solid polymer electrolyte powder (SPEP), we are able to obtain ionic conductivity values under variable conditions in order to explore the influence of external parameters on the ionic conductivity of powders. Two types of SPEs in insoluble powder form were employed in this work: (1) a proton-exchange material (SPEP-H+) based on a hyperbranched, sulfo-phenylated poly(phenylene) SPEP (HB-sPPT-H+), with measured ionic conductivity of ⁓ 210 mS cm−1 at 80 °C and 95 % of relative humidity (RH); (2) an anion-exchange conducting polymer in its chloride form (SPEP-Cl-), consisting of a radiation-grafted ultra-high density polyethylene insoluble SPEP containing covalently-bonded benzyltrimethylammonium (BTMA) head-groups, with measured ionic conductivity of ⁓ 53 mS cm−1 at 80 °C and 95 % RH.

Lithium ion conductivity, crystallization tendency, and microstructural evolution of LiZrxTi2-x(PO4)3 NASICON glass-ceramics (x = 0 - 0.4)

In this research, NASICON type (LiZrXTi2-X(PO4)3) glass-ceramics were fabricated (x = 0.1, 0.2, 0.3, 0.4). Lithium-ion conductivity along with the crystallization tendency and microstructural features were examined in this regard. Parent glasses obtained through melt quenching were converted to the glass-ceramic specimens after one-step heat treatment procedure. The resultant glass-ceramics were deeply explored by means of different techniques including scanning electron microscope, differential thermal analysis, X-ray diffractometry, and ionic conductivity measurements. According to the obtained results, presence of Zr4+ ions in the glass network and its gradual increase caused the enhanced crystallization temperature as well as declined crystallinity and microstructure coarsening. In all studied glass-ceramics, LiT2(PO4)3 solid solution was the dominant crystalline phase and Zr4+ ions partly substituted in the structure of this crystalline phase. Moreover, presence of Zr4+ ions in the glass composition resulted in diminished lithium-ion conductivity of corresponded glass-ceramics at ambient temperature. Consequently, total conductivity of specimen with the highest level of ZrO2 (x = 0.4) was measured to be 0.78 x 10-5 Scm-1, being considerably less than ionic conductivity of the base (x = 0) glass-ceramic (3.04 x 10-5 Scm-1). It seems that less crystallinity of ZrO2 containing glass-ceramics decreases required connectivity between the lithium-ion free paths and is responsible for the diminished ionic conductivity of these specimens.

Magnesium Polymer Electrolytes Based on the Polycarbonate Poly(2-butyl-2-ethyltrimethylene-carbonate).

Magnesium electrolytes based on a polycarbonate with either magnesium tetrakis(hexafluoroisopropyloxy) borate (Mg(B(HFIP)4)2) or magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2) for magnesium batteries were prepared and characterized. The side-chain-containing polycarbonate, poly(2-butyl-2-ethyltrimethylene carbonate) (P(BEC)), was synthesized by ring opening polymerization (ROP) of 5-ethyl-5-butylpropane oxirane ether carbonate (BEC) and mixed with Mg(B(HFIP)4)2 or Mg(TFSI)2 to form low- and high-salt-concentration polymer electrolytes (PEs). The PEs were characterized by impedance spectroscopy, differential scanning calorimetry (DSC), rheology, linear sweep voltammetry, cyclic voltammetry, and Raman spectroscopy. A transition from classical salt-in-polymer electrolytes to polymer-in-salt electrolytes was indicated by a significant change in glass transition temperature as well as storage and loss moduli. Ionic conductivity measurements indicated the formation of polymer-in-salt electrolytes for the PEs with 40 mol % Mg(B(HFIP)4)2 (HFIP40). In contrast, the 40 mol % Mg(TFSI)2 PEs showed mainly the classical behavior. HFIP40 was further found to have an oxidative stability window greater than 6 V vs Mg/Mg2+, but showed no reversible stripping-plating behavior in an Mg||SS cell.

Quasi-solid polyaniline/poly(vinyl pyrrolidone) blend electrolytes for dye-sensitized solar cells

Conductive polymer blend gel electrolytes can address the instability caused by liquid electrolytes in dye-sensitized solar cells (DSSCs), thereby improving their long-term stability, by reducing leakage, and enhancing electrode adhesion. This work employed in-situ polymerization to synthesize blends of polyvinylpyrrolidone (PVP) and polyaniline (PANI), which were subsequently characterized using ionic conductivity measurements, Scanning Electron Microscopy, X-ray diffraction analysis, and Fourier Transform Infrared Spectroscopy. Consequently, the optimal composition has been chosen to prepare the electrolyte solution using polymer blend, solvents, and iodine-based salts. The conductivity of blend electrolytes has also been found to be affected by the salt concentration. The fabrication of DSSCs has made use of electrolytes with the highest conductivity values. It has been found that dye-sensitized solar cells with polymer gel electrolytes are more robust but less efficient than their conventional counterparts. Solid-state dye-sensitized solar cells were found to maintain their photovoltaic performance for a duration of one week, whereas conventional cells experienced a substantial decline in short-circuit current (∼36%) and open-circuit voltage (∼33.33%) over the same period.

Optimized Thin Film Processing of Sodium Mixed Oxy-Sulfide-Nitride Glassy Solid Electrolytes for All-Solid-State Batteries

Na4P2S7–6xO4.62xN0.92x (NaPSON) glassy solid electrolytes (GSEs) were prepared and tested for their electrochemical properties and processability into thin films. The x = 0.2 composition (NaPSON-2) was found to be highly conducting, non-crystallizable, largely stable against Na-metal, and supports symmetric cell cycling up to >100 μA cm–2 without shorting. For these reasons, it was processed into thin films drawn to 50 μm and tested in symmetric and asymmetric cells. Measurements of the sodium ion conductivity using symmetric cells demonstrated that the conductivity of NaPSON-2 was unchanged by film forming. Galvanostatic cycling at 5 μA cm–2 of a 1.3 mm thick disc of NaPSON-2 showed stability over 450 h, while cycling a 50 μm thin film of NaPSON-2 showed a very slow growth in the resistance. Cyclic voltammetry and X-ray photoelectron spectroscopy of the NaPSON-2 thin film GSE revealed that it did not react with Na-metal at its surface, but rather in the bulk of the film, showing S, Na2S, and Na3P reaction products. The source of the surface stability was determined to be the preferential segregation of trigonally coordinated nitrogen. These low-cost and easily processed NaPSON GSEs provide a system of materials that could provide for significantly lower cost higher energy density grid-scale batteries.

Quasielastic neutron scattering probing H− dynamics in the H− conductors LaH3−2xOx

Using an incoherent quasielastic neutron scattering (QENS) technique, we investigate ${\mathrm{H}}^{\ensuremath{-}}$ dynamics in a series of oxyhydrides $\mathrm{La}{\mathrm{H}}_{3\ensuremath{-}2x}{\mathrm{O}}_{x}$ that exhibit characteristic high ${\mathrm{H}}^{\ensuremath{-}}$ conductivity. In the end member $\mathrm{La}{\mathrm{H}}_{3}$ ($x$ = 0), two kinds of ${\mathrm{H}}^{\ensuremath{-}}$ dynamics are identified: the jump diffusion and the localized motion. The jump length in the jump diffusion mode increases with increasing $T$. The localized motion is identified as a jump between the two inequivalent sites. These dynamics are corroborated by our molecular dynamical simulations. Our QENS data suggest that similar ${\mathrm{H}}^{\ensuremath{-}}$ dynamics occurs also in oxyhydrides $\mathrm{La}{\mathrm{H}}_{3\ensuremath{-}2x}{\mathrm{O}}_{x}$ ($x\ensuremath{\ne}$ 0), whose ${\mathrm{H}}^{\ensuremath{-}}$ concentration dependence is consistent with the previous measurement of ionic conductivity. We also discuss the possibility that $\mathrm{La}{\mathrm{H}}_{3\ensuremath{-}2x}{\mathrm{O}}_{x}$ is an example of ${\mathrm{H}}^{\ensuremath{-}}$ ion conductors governed by the concerted migration mechanism. The identified ${\mathrm{H}}^{\ensuremath{-}}$ dynamics is key to understanding the anomalous hydrogen concentration dependence of the diffusion coefficient in lanthanum hydrides, which has been a longstanding mystery in this compound.

Elucidation of Liquid Structures and Transport Properties of Highly Concentrated LiN(SO2F)2/Ethylene Carbonate Electrolytes

The Li+ conduction mechanism in highly concentrated ethylene carbonate (EC) solution of lithium bis(fluorosulfonyl)amide (LiFSA) was studied based on the measurements of thermal properties, density, viscosity, ionic conductivity, self-diffusion coefficients, Raman spectra, and proton nuclear magnetic resonance relaxation time. The compositions of EC and LiFSA were varied from dilute to concentrated states ([EC]/[LiFSA] = 9.2–0.80). For compositions of [EC]/[LiFSA] ≤ 1.5, the free solvents decrease, and contact ion pairs and aggregates become dominant, causing a significant change in the transport properties. Faster diffusion of Li+ compared with solvent (Li+ hopping conduction) was observed when the molar composition of [EC]/[LiFSA] ≤ 1.0 as in the case of sulfolane.

Quarternized polysulfone/ZSM‐5 zeolite composite anion exchange membrane separators for aluminum‐air battery

AbstractA membrane is a critical component of an Al‐air battery because it provides ion transport and ensures separation of the anode and cathode. In this work, a series of quaternized polysulfone (QPSF) membrane blended with ZSM‐5 zeolite anion exchange membranes (AEMs) were fabricated by solution casting to be used as separators in Al‐air batteries. All membranes showed moderate to excellent water uptake (WU), swelling ratio, ion exchange capacity (IEC), and ion conductivity measurements (IC). Incorporation of ZSM‐5 zeolite resulted in hydrophilicity and improved WU, with QPSF/3 wt% ZSM‐5 retaining 114% water at room temperature. The QPSF/3 wt% ZSM‐5 composite membrane was the best performing membrane with the IEC and the highest hydration number of 2.85 mmol g−1, 2.23, and a maximum of IC of 229.85 mS cm−1 at room temperature, respectively. QPSF/3 wt% ZSM‐5 retained 65% of its original IC in an alkaline medium after 7 days. QPSF/3 wt% ZSM‐5 exhibited a stable discharge voltage of 1.3 V and a specific capacity of 11,716 mAh/gAl in a laboratory fabricated Al‐air cell. This study provides an excellent anion exchange composite membrane separator candidate for Al‐air battery applications.

Use of Foundry Sands in the Production of Ceramic and Geopolymers for Sustainable Construction Materials

The aim of this research was to evaluate the possibility of reusing waste foundry sands derived from the production of cast iron as a secondary raw material for the production of building materials obtained both by high-temperature (ceramic tiles and bricks) and room-temperature (binders such as geopolymers) consolidation. This approach can reduce the current demand for quarry sand and/or aluminosilicate precursors from the construction materials industries. Samples for porcelain stoneware and bricks were produced, replacing the standard sand contained in the mixtures with waste foundry sand in percentages of 10%, 50%, and 100% by weight. For geopolymers, the sand was used as a substitution for metakaolin (30, 50, 70 wt%) as an aluminosilicate precursor rather than as an aggregate to obtain geopolymer pastes. Ceramic samples obtained using waste foundry sand were characterized by tests for linear shrinkage, water absorption, and colorimetry. Geopolymers formulations, produced with a Si/Al ratio of 1.8 and Na/Al = 1, were characterized to evaluate their chemical stability through measurements of pH and ionic conductivity, integrity in water, compressive strength, and microstructural analysis. The results show that the addition of foundry sand up to 50% did not significantly affect the chemical-physical properties of the ceramic materials. However, for geopolymers, acceptable levels of chemical stability and mechanical strength were only achieved when using samples made with 30% foundry sand as a replacement for metakaolin.